Honeybees across much of their native range are subdivided into geographic subspecies, each shaped by local climates, foraging conditions and selection pressures. The western European dark bee, the Italian yellow bee, the Carniolan bee of the Alpine region and the Iberian bee are among the better-known examples. These subspecies are not merely colour variants. They differ in overwintering strategy, swarming tendency, disease tolerance, foraging behaviour and the timing of brood production, differences that reflect genetic adaptation to specific environments. When queens from one subspecies are shipped into the range of another, mating between imported drones and local queens produces hybrid colonies whose offspring often combine traits in unpredictable ways, diluting the adaptive fit between bee and environment.

The modelling framework developed by the researchers treats honeybee populations as a dynamic genetic system influenced by several simultaneously operating forces. Migration through queen imports introduces new alleles into local populations at a rate determined by the number and origin of imported queens. Hybridisation then redistributes those alleles across subspecies boundaries through mating. Drift, the random fluctuation of allele frequencies that is especially powerful in small or fragmented populations, acts in the opposite direction, while selection favours combinations of genes that perform well under local conditions. By representing these forces mathematically, the model can project how a local bee population changes genetically over time under different import scenarios.

A central insight from the analysis is that the genetic consequences of imports depend less on the volume of bees moved than on the pattern of movement and mating. Sporadic imports of non-native queens into a large, genetically diverse local population may leave little lasting signature, because hybrid offspring mate with local drones and their foreign alleles are progressively diluted. Sustained, large-scale importation, by contrast, can swamp local gene pools, particularly when imported queens produce drones that dominate the mating opportunities available to virgin queens in the area. Because honeybee queens mate with many drones in flight, often from colonies within a several-kilometre radius, a cluster of non-native colonies can exert disproportionate influence on the genetics of every hive in the neighbourhood, including wild and feral colonies that no beekeeper manages directly.

The model also highlights the role of time lags. Genetic erosion of native subspecies does not happen in the season the imports arrive. It accumulates as hybrid alleles recombine and spread through successive generations, a process that can take decades to become obvious. By the time a beekeeper or breeding association notices that the distinctive traits of a local strain have faded, the underlying allele frequencies may have shifted substantially and irreversibly. This slow, cumulative dynamic is precisely the kind of phenomenon that is difficult to detect through routine hive inspections but readily captured by a population genetic model that tracks allele frequencies over long time horizons.

Not all consequences of hybridisation are negative from a practical standpoint. Crosses between subspecies are known to sometimes display heterosis, or hybrid vigour, with increased productivity and colony growth. Imported subspecies such as the Italian bee are prized for honey yields and gentle temperament, while Carniolan bees are valued for rapid spring build-up and low swarming. The modelling work does not dismiss these benefits. Instead, it frames them against a longer-term accounting: hybrid vigour may boost short-term performance, but continued introgression of non-native genes can undermine the locally adapted traits that make native bees resilient to regional climates, parasites and nectar flows. The balance between these outcomes depends on import rates, the reproductive success of hybrids and the strength of local selection.

One of the most consequential findings concerns the interaction between imports and conservation programmes. Many European countries have established conservation zones where only native subspecies are supposed to be kept, in an effort to preserve genetic resources that may prove valuable as climate change alters disease pressures and foraging conditions. The model shows that such zones are vulnerable to gene flow from surrounding areas. Because drones fly freely across zone boundaries and beekeepers within or near protected areas sometimes continue to use imported stock, even well-intentioned conservation efforts can be undermined by continuing introgression. The framework allows managers to estimate how large a conservation zone must be, and how strictly imports within and around it must be controlled, to keep hybridisation below a threshold that would compromise the genetic integrity of the protected population.

The study’s approach also speaks to a long-standing difficulty in honeybee science: distinguishing the effects of managed imports from those of natural gene flow. Historically, honeybee subspecies diverged in relative isolation across mountain ranges, seas and climatic gradients, and natural hybrid zones formed narrow contact areas where subspecies met. Modern beekeeping has collapsed those distances. Trucks carrying thousands of queens each season, migratory hives moved for pollination contracts and the global trade in packaged bees have created gene flow patterns with no historical precedent. The model provides a way to quantify how this artificial connectivity compares with the natural gene flow that shaped subspecies diversity, and at what point human-mediated mixing begins to dominate.

For beekeepers, the practical message is nuanced. The research does not argue that all imports should stop; imports have real value in restocking colonies lost to disease, improving genetic diversity within small breeding populations and accessing desirable traits. Rather, the model suggests that imports work best when they are deliberate, documented and spatially managed. Concentrating imported stock in areas separated from conservation zones, monitoring the genetic composition of local populations with molecular tools and preferring queens bred from locally adapted stock where possible can preserve choice for future generations of beekeepers. The alternative, uncontrolled and continuous mixing, risks a landscape of genetically uniform bees whose performance depends entirely on intensive management, an outcome the authors describe as a loss of both biological and economic resilience.

As pressures from varroa mites, habitat loss and climate change intensify, the genetic resources embedded in native honeybee subspecies may become one of the most valuable assets available to apiculture. Locally adapted populations represent standing variation in traits such as disease resistance and overwintering survival that breeding programmes cannot easily recreate once lost. The modelling framework presented in Heredity offers researchers and policymakers a quantitative tool for weighing the immediate benefits of queen imports against the long-term costs of hybridisation, replacing a debate that has often run on anecdote and regional tradition with projections grounded in population genetics. Whether that tool is adopted before further genetic erosion occurs will depend on whether the fragmented world of beekeeping, with its competing commercial and conservation interests, can act on what the mathematics now makes plain.

Subject of Research: Population genetic modelling of honeybee queen imports and hybridisation between native and non-native subspecies

Article Title: Modelling the impacts of imports and non-native subspecies hybridisation in honeybees

Article References: de Carlos, I., Strachan, L., McCormack, G. P., Gorjanc, G., & Obšteter, J. (2026). Modelling the impacts of imports and non-native subspecies hybridisation in honeybees. Heredity. https://doi.org/10.1038/s41437-026-00878-x

Image Credits: AI Generated

DOI: 10.1038/s41437-026-00878-x

Keywords: honeybees, queen imports, hybridisation, subspecies, population genetics, genetic erosion, conservation zones, apiculture, local adaptation, gene flow, Heredity, bee breeding